Humane Endpoints

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Humane endpoint refers to the point at which an experimental animal's pain and/or distress is terminated, minimized or decreased. It includes actions such as humane killing, terminating a painful procedure and giving treatment to relieve pain and/or distress. Using humane endpoints in animal protocols is a refinement and provides an alternative to using death or severe signs of animal pain and distress. They are essential in those situations with a strong potential for pain and distress (e.g., acute toxicology, or animal models of infection, cancer or inflammatory disease). However, a humane endpoint in a scientific study also ensures that the scientific goal of the study is reached.

Humane endpoints are established before the start of a study.

Selecting a Humane Endpoint

A moribund animal is one that is close to death and may be unresponsive, for example, to stimuli, exhibit dyspnea (breathlessness), hypothermia, prostration. However, once the point of being moribund is reached, detailed observations can help to set an earlier experimental endpoint.

Steps to develop humane endpoints include:

  • considering the experimental goal and what might be the earliest observable indicators of that effect prior to signs of animal pain and/or distress
  • considering that it may not be necessary to reproduce a condition or effect in detail (and potential severity) as may be seen in humans (for example, using animals to study arthritis may not actually require chronic painful joint disease to be manifested, just an increase or decrease in urinary excretion of cartilage breakdown products to be measured)
  • developing specific endpoints for each experiment after consulting references on humane endpoints and a clinical veterinarian, to determine likely adverse effects and clinical signs
  • making observations of the animals (e.g., behaviour, physiology) to determine which are the most significant indicators of pain and/or distress in the specific circumstances of the research
  • determining which observations are the most significant predictors of further deterioration in the animal's condition, and identify the earliest point at which those signs appear, monitoring and recording the use of humane endpoints during the experiment using pilot studies with small numbers of animals to determine the onset and progress of adverse effects and identify early scientific and humane endpoints
  • including all information about humane endpoints used when publishing the results of the study
  • ensuring appropriate training for staff who are monitoring animals for signs of adverse effects

Humane Endpoint Score Sheets

Using observational checklists or score sheets for scoring an animal's condition in a study provides an objective basis for decisions about endpoints. Score sheets help ensure that specific observations are not overlooked and help improve observational skills, particularly with the smaller laboratory animals. However, score sheets do not cover all abnormalities or observations, and cannot replace a thorough examination of the animal.

This section has been adapted from the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) website and CCAC guidelines.